Kansas had a blast of very cold temperatures a couple of weeks ago that may damage fruit plants. Peach trees often have fruit bud damage when temperatures reach 5 to 10 degrees below zero. The tree will be fine as the leaf buds are undamaged. Note that damage to fruit buds are progressive. In other words, a temperature of minus 10 for a short period will cause less damage than a sustained reading of 10 below zero. Also, the buds will show progressively more damage the further below minus 10 degrees the temperature reaches.

Thornless blackberries also can be damaged at 5 to 10 degrees below zero but this is variety dependent as some of the newer thornless varieties are more hardy. Also, thorny types are often more hardy than the thornless types. With blackberries, we are not worried about the fruit buds but the fruiting canes. Cold temperatures can kill all aboveground growth. However, the plant will survive and grow new canes from the crown that will fruit next year.

Apples are hardier, and fruit buds are usually not damaged unless the temperature reaches minus 20 to minus 25 degrees. Red Delicious is one of our most tender varieties and can be damaged when temperatures reach minus 15. As with peaches, the tree will be fine at these low temperatures; only the fruit buds are at risk.

What about wind chill damage to fruit plants? Wind chills can have a profound effect on warm-blooded animals' ability to keep warm. Plants do not respond to wind chill indexes the same as warm-blooded animals because they do not need to maintain a temperature above that of their surroundings. For example, a wind chill of 40 degrees below zero at a temperature of zero degrees Fahrenheit will not cause any more cold injury to plant tissue than a wind chill index of 20 degrees below zero at zero degrees Fahrenheit. Although cold temperatures may not damage plants, wind can desiccate (dry out) plant tissues. Plant tissues require moisture to survive, and high wind velocity can cause moisture loss. This desiccation may be great enough to injure or even kill tissue, particularly the smaller size wood as in peach twigs, apple spurs or blackberry canes. There is no scientific evidence to show that an increasing wind chill index will directly increase plant damage due to cold injury.